Question

这个类模版哪里有问题？VC++6.0

template <typename t>
class complex
{
protected:
t real, image;
public:
complex(t r1 = 0, t i1 = 0)
{
real = r1;
image = i1;
}
template <typename t>
friend ostream &operator<<(ostream &output, const complex<t> &c)
{
output<<"complex: "<<c.real<<'\t'<<c.image<<endl;
return output;
}
};

D:\我的文档\MyProject\example\10\10_08\10_08.cpp(19) : error C2562: '<<' : 'void' function returning a value
D:\我的文档\MyProject\example\10\10_08\10_08.cpp(16) : see declaration of '<<'
D:\我的文档\MyProject\example\10\10_08\10_08.cpp(26) : see reference to function template instantiation 'void __cdecl operator <<(class std::basic_ostream<char,struct std::char_traits<char> > &,const class complex<int> &)' being compiled
执行 cl.exe 时出错.

Answer 1

输入输出流>>，<<的重载的实现语句要放在类定义里，这个比较特殊。把下面的代码移到定义语句里，就可以了。
ostream& operator<<(ostream& os,const Time& t)
{
os<<"hours is: "<<t.hours<<" ,minutes is: "<<t.minutes<<endl;
return os;
}

追问

应该还有friend，我把template 给去了，并在类定义了友元函数。就没出错了